1. Field of the Invention
The present invention relates to switching systems and methodologies. More specifically, the present invention relates to optical and electronic crossbar switching circuits, systems and techniques.
2. Description of the Related Art
A generic crossbar switch allows an incoming signal to a switch port to be directed (switched) to any other port. Crossbar switches are used in radar and numerous other applications to distribute radio frequency and/or digital signals from one source (e.g., an antenna) to multiple destinations (e.g., processors) and vice versa. Previously, crossbar switching was implemented electronically. However, these systems are hampered by capacitive effects and distance limitations and are typically limited to digital signals. Prior optical crossbar switching systems have been also been limited to digital signals.
Hybrid arrangements use a combination of electronic and optical switching elements. However, hybrid crossbar switching systems require a large number of connectors. Further, historically, these connectors have been found to be somewhat unreliable.
For radar and a number of other applications, there is currently a need to switch a large number of high frequency analog signals (e.g., signals in the 100 gigahertz range) between a number of processors and hundreds or thousands of elements of an antenna array.
Accordingly, a need remains in the art for an improved system or method for crossbar switching of high-speed digital analog signals. There is a particular need for a system or method for crossbar switching of high frequency analog signals.
The need in the art is addressed by the switch module and backplane designs of the present invention. The inventive module includes a first filter for providing a single input/output port, a transmitter for launching a signal through the port in a first direction, and second filter for receiving signals from the port in a second direction, the second direction being opposite from the first direction.
In a specific implementation, the module further includes plural receivers connected to the second filter for receiving the signals through the port. In the illustrative embodiment, the transmitter is an optical transmitter, the receiver is a photodetector, and the first and second filters are optical filters. The transmitter may be a tunable laser and the system may be implemented with wavelength modulation. In the illustrative embodiment, an arbitration circuit is provided to regulate data transmission and reception.
When complemented with an interconnect mechanism, the module is part of a novel crossbar switch design. In the preferred embodiment, the interconnect mechanism is a backplane having n input/output ports adapted to communicate with the ports of the modules. Specifically, the backplane includes n first filters, each first filter being coupled to a respective one of the backplane ports, and n coupling elements. The coupling elements may be second filters. In any event, an output of each of the n first filters is connected a respective one of the n coupling elements. The backplane further includes n splitters, each splitter being coupled to an input of a respective one of the n first filters on one end and to a unique set of n coupling elements on another end thereof. The unique set of coupling elements includes all of the n coupling elements except the respective one of the coupling elements to which each the corresponding first filter is output coupled.
Many alternatives for the interconnect mechanism are proposed including a single optical fiber, a lens disposed on each of the modules, a diffusion plate, a holographic lens, or a matrix of optical fibers.
The switches may be interconnected with bridging circuits to provide a network or interconnect fabric. The bridging circuit may include at least two input/output ports, a first optical filter coupled to each of the input/output ports, an optical transmitter coupled to each of the first filters, and a second optical filter coupled to each of the first filters. Plural detectors are connected to each of the second optical filters and a multiplexer is connected to each of the detectors and each of the optical transmitters.
In addition to optical filters, the use of time division multiplexing (TDM) and code division multiple access (CDMA) implemented either electrically or optically can be used to increase the number of independent users that the distributed switch handles.
The purpose of the invention is to provide digital high data rate or high frequency analog transmit and receive interconnections between and within units that are interconnected via a backplane interconnecting structure or fabric made up of a single fiber with optical filtering.